OK, as far as I can remember a script (as any other text) used to be written in a typewritter (as many authors still do all they work) so... the "font" used in any typewritter used to be some kind of courier type.
Now... I really can't recall good enough (this is editorial design... I took this class almost 9 years ago and computer design now is different) every page supposed to have the same number of keystrokes in a standart of 8x11 inches, single spaced pages (there was a even a line count of keystrokes including letters and spaces) so at the end you had a page of let's say 30 lines consisting of 90 keystrokes equals 2700 keystrokes.
This was used to know like a raw aproximate of the lenght of a text and this number was used to determine how much space do the lenght of the text was going to take in a design space, cause every font had this sort of index number (a percentage of the lenght of every letter and space depending on the design of the font... that's why your text gets longer and shorter when you change font... that index is embedded in every font used in a computer nowdays) so... in industry standart you are supposed to use a courier type in 12 pts at single space in a 8x11" paper.
Don't get confused... one thing is how long your work is in matter of "author pages" and other is the design and type to be used... if you are going to get publiushed, you'll get a preliminary test and see how long it ends up, but that's the designers work.... so no worries.
Rock on Bro.
Power corrupts. Absolute power is kinda neat.